“I can’t select the surface when I want to start drawing a line from the surface.”
You need to use the OnSurface (OnSrf) or PersistantOnSurface (POnSrf Osnap). OnSrf is “one shot” and good for making one selection. POnSrf is “persistent” and last until the command is completed.
OnSurface (OnSrf)
Snap to and track over a surface for one pick.
OnSurface example
Place a point object on a surface.
OnSurface steps
- Select the surface.
The marker moves only over the surface. - Click the left mouse button to place the point.
If you are tracking over a polysurface, the marker is restricted to the single selected face. The cursor changes shape to indicate that you cannot pick. To track over the whole polysurface, see the OnPolysrf object snap.
To access this object snap on the Osnap control
- Press and hold the Ctrl key and hover the mouse over the Osnap control.
PersistentOnSurface (POnSrf)
Snap to and track over a surface until the command completes.
To access this object snap on the Osnap control
- Press and hold the Ctrl key and hover the mouse over the Osnap control.
Percentage (Percent)
The selected curve is marked with temporary black points that can be snapped when the Point object snap is disabled.
If the percentage is less than 50, the curve is marked with multiple snap points. For example, when using 30, you get snap points at 30%, 60% and 90%.
To access this object snap on the Osnap control
- Press and hold the Shift key and hover the mouse over the Osnap control.